Hydraulic shock damping apparatus



Sept. 22, 1959 D. E. OYSTER HYDRAULIC SHOCK DAMPING APPARATUS Filed Jan. 23, 1956 INVENTOR.

DUANE E. OYSTER United States Patent HYDRAULIC SHOCK DAMPING APPARATUS Duane E. Oyster, Galloway, Ohio, assignor, by mesne assignments, to American Brake Shoe Company, New York, N.Y., a corporation of Delaware Application January 23, 1956, Serial No. 560,515

4 Claims. (Cl. 137-108) This invention relates to hydraulics and more particularly to a hydraulic system which may be employed with facility, for example, for starting a hydraulic motor gradually and smoothly and without hydraulic shock to any part of the hydraulic system and particularly without shock to the motor or the apparatus driven thereby. In another aspect, the invention relates to valve apparatus which may be employed in a hydraulic system to produce the results set forth above.

An object of the invention is to provide an improved and simplified hydraulic system which may be employed, for example, to start a motor gradually and smoothly.

Another object of the invention is to provide an improved valve apparatus which may be employed in a system such as set forth to accomplish the stated improved results.

Another object of the invention is to provide improved valve apparatus in which a control valve means is operated to close gradually in response to increases in pressure in a conduit associated therewith and connected, for example, to supply fluid to a motor to drive the latter.

Still another object of the invention is. to provide improved and simplified construction in a valve apparatus of the type set forth in the foreging object.

Further objects and advantages of the present invention will be apparent from the following description, reference being bad to the accompanying drawing wherein a preferred form of embodiment of the invention is clearly shown.

The accompanying single figure of the drawing is a diagrammatic illustration of a hydraulic system including the features of the invention and in which a pres- .sure responsive valve apparatus which also includes features of the invention is shown in section.

Referring more particularly to the drawing, the hydraulic system includes a reservoir or tank for hydraulic liquid, a constantly driven positive displacement type hydraulic pump 11 which receives hydraulic liquid from tank 10 through a conduit 12 and is connected through a conduit 13 to supply hydraulic liquid under pressure to an open center four-way valve 14 and a. pressure responsive control valve 15. Four-way valve 14 is connected through conduits 16 and 17 with a reversible hydraulic motor 18 and also to tank 10 through a conduit 19.

The four-way valve 14 is manually operated by a pivotally mounted lever 20 and it is. known in the art as an open center valve because its construction is such that when its core or spool 21 is in its center or neutral position, as shown in the drawing, all of the liquid received from the pump 11 through conduit 13 is returned to tank 10 through conduit 19' and the motor 18 is not driven.

Referring more specifically to the construction of fourway valve 14, this valve includes a body 22 provided "ice with end caps 23 and 24 and a bore 25 in which the 7 core or spool 21 is received. The body 22 includes five spaced annular grooves 26, 27, 28, 29 and 30 which surround the bore 25 and the core or spool 21 and these grooves are connected respectively with conduits 19, 16, 13, 17 and 19. The core or spool 21 is provided with a central land 31 which is flanked by peripheral grooves 32 and 33 formed in the core or spool 21 and the arrangement and spacing of said grooves 2630, land 31 and grooves 32 and 33 is such that when the core or spool 21 is in its center or neutral position, as shown in the drawing, all of the grooves 2630 are interconnected.

Assuming that conduit 13 is blocked at the pressure responsive control valve 15 and the core or spool 21 is in its neutral position, the operation of that portion of the system above described is as follows: pump 11 is driven by any suitable prime mover, not shown, to deliver hydraulic liquid from tank 10 through conduits 12 and 13 to groove 28 in valve body 22. Hydraulic liquid upon entering bore 25 from groove 28 will flow through the bore 25 to grooves 26 and 30 and be returned to tank 10 through conduit 19. It will be seen that at this time motor conduits 16 and 17 will also be connected to tank 10 through the grooves 27 and 29, bore 25 and conduit 19 and, therefore, that the motor 18 will be at rest. It will also be seen that because the hydraulic liquid being pumped by pump 11 is directed to tank 10 by valve 14 that the pressure of this hydraulic fluid will correspond, substantially, with the atmospheric pressure.

Assuming now that it is desired to cause the motor 18 to be driven in a forward direction, the lower end of lever 20 is swung to the position indicated at F in the drawing which, of course, causes the core or spool 21 to be shifted to its left-hand position, not shown, in bore 25. When core or spool 21 is in its left-hand position, hydraulic liquid entering the valve body from pump 11 through conduit 13 is directed from groove 28 by groove 33 in the core or spool 21 to the groove 29 and through conduit 17 to motor 18. Hydraulic liquid exhausted from motor 18 passes through conduit 16 to groove 27 from which it is directed by groove 32 to groove 26 and tank 10 through conduit 19.

When it is desired to cause the motor 18 to be driven in a reverse direction, the lever 20 is swung to the position indicated at R to shift the core or spool 21 to its right-hand position. In this position, the core or spool 21 directs hydraulic liquid from groove 28 to groove 27 and motor conduit 16. Exhaust liquid flowing from the motor 18 passes through conduit 17 to grooves 29 and 30 and tank 10 through conduit 19.

The hydraulic apparatus and system thus far described, except the mentioned pressure responsive control valve mechanism 15 which is described in detail hereinafter, is conventional and it has been found that when the valve core 21 of valve 14 is shifted quickly from its neutral position to either its right or left-hand position that violent hydraulic shocks occur in the hydraulic system which are detrimental to the elements which comprise the system and particularly to the pump 11 and motor 18 thereof. These shocks are created by the sudden diversion by valve 14 of the entire output volume of pump 11 to motor 18 and the tendency of the motor to block the flow of said liquid, which of course, causes the pump to increase the hydraulic pressure in the system quite rapidly, in fact almost instantaneously. Such sudden increases in the hydraulic pressure places undue strain upon every part of the high pressure portion of the system and causes the motor 18 to be set in motion rapidly at maximum horsepower output. Such condition is highly undesirable since in addition to overloading parts of the hydraulic system it causes any mechanism which is driven by the motor to be set in motion with a violent jerk.

In order to overcome the above mentioned, and very serious problems I have designed the pressure responsive shock damping valve apparatus 15 and incorporated it into the system above described. This apparatus 15 prevents the above described shocks and sudden starting, of motor 18 by causing the pressure in conduits. 13 and 16 or 13 and 17, as the case may be, to increase gradually regardless of the rapidity with which the core or spool 21 of valve 14 is shifted from its neutral position and it has the further function of acting in the capacity of a; relief valve to limit the maximum hydraulic pressure which may be created in the conduit 13.

The pressure responsive shock damping valve apparatus 15 includes a body 35 inthe form of a casting machined to include a plurality of bores. Among these bores is a high pressure port or passage 36 to' which the conduit 13 is connected'and a low pressure exhaust port or passage 37 which is connected with an exhaust or return conduit 38 leading to tank 10. The ports or passage ways 36 and 37 are interconnected by a stepped bore 39 in which a hardened valve seat 40 is positioned between the bores 36 and 37. One end of the stepped bore is closed by a plug 41 and its other end forms a cylinder which is closed by a plug 42. A piston 43 including an integral valve stem 44 is contained within the cylinder and divides it into two chambers 45 and 46. The valve stem 44 is urged to close the valve seat 40 by a compression spring 47 contained within the chamber 46 and abutting the plug 42 and piston 43 thereby to isolate the high and low pressure ports or passageways 36 and 37 from each other.

The chamber 45 is directly connected to the pressure port or passage 36 and with the chamber 46 through a restrictor orifice 48 formed in the piston 43. The function of this restrictor orifice 48 will be set forth fully hereinafter. The chamber 46 communicates through bores 49 and 50 with one end of the low pressure or exhaust port passage 37 and the bore 50 contains a spring loaded valve 51 including a seat 52 and a poppet 53 between the bore 49 and passageway 3-7. The low pressure or exhaust passageway 37 is provided with a restrictor orifice which prevents chattering of the poppet 53 and valve stem 44 upon their seats. The bore 50 extends completely through the valve body 35 and is closed at its lower end by a plug and at its upper end it terminates in an internally threaded portion which receives the lower threaded end of an adjusting sleeve 54 for the valve 51.

The top of the valve body 35 is provided with a cap 55 which includes a bore through which the sleeve 54 extends and with which it is sealed in liquid tight relation .by -a pair of O-rings 56 carried in spaced grooves formed in the sleeve 54. Sleeve '54 forms a cylinder for a piston 57 and it includes an inwardly extending shoulder 65 at its lower end for limiting the movement of said piston toward the valve 51 and against a compression spring 58 interposed between the bottom of the piston 57 and poppet 53. The upper end of the cylinder in sleeve 54 is closed by a plug and the sleeve 54 is provided with a peripheral groove 59 and it is connected through a plurality of radially extending bores in the sleeve wall with 2 1; piston chamber therein at the upper end of the piston The body 35 also includes a small diameter bore 60 which extends from the high pressure port or passage 36 and chamber 45 to a small diameter bore 61 in cap 55 which intersects a stepped bore 62 leading to the bore in cap 55 and connecting with the chamber in sleeve 54 through the channelor groove 59 formed therein. A restrictor element 63 having an orifice of very small diameter is held in the bore 62 by a compression spring 64 which abuts said restrictor element and a plug in 0116 K nd of the bore 62.

Before describing the operation of pressure responsive control apparatus 15, it is pointed out that when the apparatus is not in operation the piston 57 and spring 58 exert very little, if any, pressure on the poppet 53 to close valve 51 and that the spring 47 urges the stem 44 of piston 43 into the valve seat 40 to close the latter and isolate the high and low pressure ports or passageways 36 and 37 from-eaeh-other. Spring 47 need only supply suificient force, for example twenty pounds, to insure that the stem 44 will engage the valve seat' 40 with sufficient force to insure no leakage of hydraulic liquid from the high pressure port or passageway 36 to the low pressure port or passageway 37;

When the pressure responsive control apparatus 15 is in operation, its bores and passageways are filled with hydraulic liquid and hydraulic liquid may be fed through conduit 13 to the high pressure port or passageway 36. Assuming that this hydraulic liquid is under little or no pressure its flow, except for a small quantity which may pass through the orifice 48 in piston 43, will be blocked by the control valve including the valve seat 40 and valve stem 44. The above described condition will exist when the core-or spool 21 of valve 14 is in its neutral position and upon the shifting of the core or spool 21 from its neutral posit-ion the pressure in conduit 13 and consequently high pressure port or passageway 36 will increase rapidly.

Anincrease in pressure in the high pressure passageway 36 and chamber 45 su-flicient to overcome the spring 47 will cause the piston 43 and valve stem 44 to move away from the valve seat 40 and open the latter whereby substantially the entire output volume of the pump 11 will flow, at least momentarily, to the high pressure passageway 36, through the valve seat 40 and the low pressure or exhaust port or passageway 37 and conduit 38 to tank 10. Piston 43 can move into the chamber 46 as above described because at this time the liquid in chamber 46 can flow to the low pressure or exhaust port 37 through the passages 49 and 50 and the open valve 51. It will be seen that the pressure in chamber 45 will be reflected at a retarded rate to the top of piston 57 through the bores 60, 61, 62, orifice 63, groove 59 and the radial bores in sleeve 54 associated therewith and that as the pressure above the piston 57 increases and causes the piston 57 to exert pressure on the spring 58 and poppet 53 to close the valve 51 that the flow of liquid from the chamber 48 to exhaust passage 37 will berestricted whereby the pressure in chamber 46 will increase gradually; As the pressure in said chamber increases, the differential -'m pressures between .the opposite ends of piston 43 decreases and spring 47 will move the piston 43 and valve stem 44 slowly and in proportion to the rate of increase in pressure in the chamber 46 toward the valve seat 40 thereby closing the valve seat slowly and gradually restricting the flow of liquid from port or passage 36 to port or passage 37.. Because of the action or function of the restrictor orifice 63 in retarding or causing the increase in pressure above the piston .57 to lag the pressure in the chamber 45 the closing of the valve seat 40 will be gradual and when the piston '57 is moved into engagement with a shoulder 65 on the bottom of sleeve 54 the maximum closing pressure exerted upon poppet 53 will be attained.

Should the pressure in chamber 46 exceed the maximum pressure setting of valve 51 and cause the latter to open, the pressure in chamber 45 will cause the piston 43 to withdraw the valve stem from seat 40 to permit all of the output of pump 11 to pass through conduit 13, passageway 36, valve seat 40, exhaust port or passageway 36 and conduit 38 to tank' 10. At this time the apparatus is functioning as a relief valve.

The maximum pressure at which the valve 51 will open to cause the apparatus to function as a relief valve may befadjus'ted' by rotating the sleeve 54 to thread it into or out of the body 35 thereby to change the position of the shoulder 65 and rotation of the sleeve 54 is prevented by a lock nut 66 on the sleeve which may be tightened against the cap 55.

From the foregoing description, it will be seen that I have provided an improved pressure responsive control apparatus which when inserted in a system of the character set forth will prevent the creation of hydraulic shocks in the system and their resultant detrimental efiects to its elements and which will cause the system to start a motor or any other device to which it supplies hydraulic liquid gradually and without detrimental effects.

While the form of embodiment of the present invention as herein disclosed constitutes a. prefered form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

I claim:

1. A hydraulic shock damping valve including a body having a high pressure inlet and a low pressure outlet passage; a valve between said passages; a chamber; piston means in said chamber connected to operate said valve, said piston means having opposite ends exposed to pressure in said high pressure passage and pressure in said chamber respectively; means acting to move said piston to close said valve; restrictor means between said high pressure passage and said chamber whereby pressures may be balanced between them; relief valve means for exhausting said chamber thereby to permit pressure in said high pressure passage to move said piston to open said valve, and pressure operated means operating in response to an increase in pressure in said high pressure passage to resist opening of said relief valve.

2. A hydraulic shock damping valve including a body having a high pressure and a low pressure passage; a valve between said passages; a chamber; piston means in said chamber connected to operate said valve, said piston means having opposite ends exposed to said high pressure passage and said chamber respectively; means acting to move said piston to close said valve; restrictor means between said high pressure passage and said chamber whereby pressure may be balanced between them; relief valve means for exhausting said chamber thereby to permit pressure in said high pressure passage to move said piston to open said valve, and pressure operated means operating in response to an increase in pressure in said high pressure passage to resist opening of said relief valve, said last named means including a valve; a spring acting on said valve; a piston acting on said spring; a chamber for said piston, and means connecting said last mentioned chamber with said high pressure passage.

3. A hydraulic shock damping valve including a body having a high pressure and a low pressure passage; a Valve between said passages; a chamber; piston means in said chamber connected to operate said valve, said piston means having opposite ends exposed to said high pressure passage and said chamber respectively; means acting to move said piston to close said valve; restrictor means between said high pressure passage and said chamber whereby pressures may be balanced between them; relief valve means for exhausting said chamber thereby to permit pressure in said high pressure passage to move said piston to open said valve, and pressure operated means operated in response to an increase up to a predetermined pressure in said high pressure passage to resist opening of said relief valve.

4. A hydraulic shock damping valve including a body having a high pressure and a low pressure passage; a valve between said passages; a chamber; piston means in said chamber connected to operate said valve, said piston means having opposite ends exposed to said high pressure passage and said chamber respectively; means acting to move said piston to close said valve; restrictor means between said high pressure passage and said chamber whereby pressures may be balanced between them; relief valve means for exhausting said chamber thereby to permit pressure in said high pressure passage to move said piston to open said valve; pressure operated means operated in response to an increase up to a predetermined pressure in said high pressure passage to resist opening of said relief valve, and means for adjusting said predetermined pressure.

References Cited in the file of this patent UNITED STATES PATENTS 1,934,758 Temple Nov. 14, 1933 2,368,754 Ernst Feb. 6, 1945 2,420,554 Mott May 13, 1947 2,451,013 Ziskal et al. Oct. 12, 1948 2,573,864 Moran Nov. 6, 1951 2,649,688 Slomer Aug. 25, 1953 

